Rotary pump



Feb. 6, 1968 R- S. LOMBARD ROTARY PUMP Filed Aug. 26, 196

3,367,274 ROTARY PUMP Ralph S. Lombard, Stamford, Conn, assignor toTextron, Inc, Providence, ILL, a corporation of Rhode Island Filed Aug.26, 1966, Ser. No. 575,322 6 Claims. (Cl. 103-103) The present inventionrelates to rotary pumps and particularly to self priming pumps capableof handling liquids containing solid pieces or particles. Such pumps areuseful, for example, in pumping water from ditches or excavations wherestones or other solid objects may be drawn in through the suction lineof the pump.

A rotary pump of the kind of which the invention relates comprises animpeller rotating in a housing or casing having inlet and dischargepassages. The impeller is mounted on a shaft driven by a suitable motor,for example an internal combustion engine.

When a pump of this kind is used to pump water or other liquidcontaining solids, for example sticks or stones, considerable damage maybe done in the event a solid object jams or wedges between the impellerand the housing. Since the driving motor has a considerable amount ofrotational inertia, high forces are generated when the impeller issuddenly jammed or blocked. This may result in breaking the impeller orhousing or other serious damage to the pump or to the engine driving thepump.

The present invention is directed to the problem of overcoming thisdifficulty and protecting the pump and engine from damage when suchblocking or jamming by a solid object occurs. The problem is complicatedby the fact that in order to provide good self-priming characteristics,the radial and axial clearances between the rotor and portions of thehousing must be carefully selected and rigidly maintained. Hence,conventional flexible connections permitting considerable relativemovement are not satisfactory. Moreover, in order to maintain highvacuum in the final stages of priming, the impeller must be mounted onthe shaft in such a way as to avoid any air leakage that would dissipatethe vacuum.

In accordance with the invention, there is provided a novel rotary pump,and in particular a novel mounting of the pump impeller on the driveshaft, which makes it possible for the pump to be blocked or jammedrepeatedly by solid objects drawn in through the pump intake withoutmaterial damage to the pump or to the impeller mounting or engine. Forexample in tests, pumps in accordance with the invention have been foundcapable of withstanding repeated jamming by used spark plugs fed intothe liquid intake of the pump.

The nature and characteristics of the invention will be more fullyunderstood from the following description of a preferred embodimentshown by way of example in the accompanying drawings in which:

FIG. 1 is a longitudinal sectional view of a pump and a portion of anengine by which the pump is driven.

FIG. 2 is an enlargement of a portion of FIG. 1 showing in more detailthe mounting of the impeller on the drive shaft and,

FIG. 3 is a perspective view of a bushing incorporated in the impellermount.

In the drawings, a pump P in accordance with the invention is shownmounted on an internal combustion engine E by which the pump is driven.The engine B (only a portion of which is shown in the drawing) comprisesa housing or casing 10 with a cylinder 11. A crankshaft 12 is rotatablymounted in the housing by suitable bearings of which two are shown at 13and 14 as ball bearings having inner and outer raceways. The bearingsrotatably supoprt the shaft radially and also position it in an axialdirection. The housing includes a crankcase portion 15 containing acrankpin 16 on a counter-weighted States Patent f 3,367,274 PatentedFeb. 6, 1968 crank disc 17 which is integral with, or fixed on, theshaft 12. The crankpin 16 is connected by a suitable connecting rod.(not shown) to a piston (not shown) reciprocating in the cylinder 11. Afan 18 having a hub portion 19 is keyed on the shaft 12 and is securedby a nut 21 screwed onto a threaded portion 12a of the shaft 12. The hubportion of the fan bears on the inner race of the hearing 13 which isspaced by a sleeve 22 from the inner race of bearing 14 which in turnabuts the crank disc 17 so as to position the assembly in fixed positionon the shaft 12. The nut 21 provides a shoulder on the shaft forpositioning the impeller of the pump as will appear below. A shim orwasher 23 is shown interposed between the nut 21 and the hub portion 19of the fan. The shaft 12 is provided with suitable oil seals of whichone is shown at 24. Other portions of the engine which are not neededfor an understanding of the present invention are not shown ordescribed.

The pump P has a casing or housing 25 which is shown as comprising aback plate 25a including a housing for the fan 18, an impeller chamber25b having a suitable volute passage and an end plate 25c. The severalparts of the housing are assembled and secured together by suitablemeans such as screws or bolts (not shown). Fluid tight seals between theportions of the housing are provided by O-rings 26, 27 and 28 and by aNeoprene washer 29. The pump casing is likewise mounted on the engine Eby suitable bolts or other means not shown. The pump housing is providedwith a suitable intake or inlet opening 31, discharge opening 32 anddrainage opening 33, normally closed by a suitable plug.

The pump P further comprises an impeller 35 which is mounted on anddriven by the shaft 12 and is rotatable in the impeller chamber 25b ofthe pump housing. The impeller 35 comprises a hub portion 35a, a backplate or body portion 35b, and one or more vanes 350 of generally spiralconfiguration. In order to assure efficient operation of the pump andachieve effective priming, it is important to provide close clearancesbetween the impeller and the wall of the impeller chamber as indicatedat 36 and also between the periphery of the impeller and the cutoff orbreakwater (not shown) of the volute portion of the impeller chamber.

A fluid tight seal between the hub portion of the impeller and thehousing is provided by a sealing ring 41 carried on and rotating withthe impeller hub and pressed by a spring 42 against a stationary ring 43set into an annular recess in the housing. An O-ring 44 provides a sealbetween the housing and the ring 43. A bellows-like diaphragm 45provides a seal between the sealing ring 41 and the hub portion of theimpeller while permitting axial movement of the ring 41 under pressureof the spring 42.

The hub 35a of the impeller 35 has a central bore comprising acylindrical portion 46a which receives and closely fits an end portionof the shaft 12, an intermediate cylindrical portion 46b of smalldiameter and a fursto conical or tapered portion 460 which increases indiameter in a direction toward the outer end of the impeller hub. Beyondthe tapered bore portion 46c there is a counter bore or recess 46d oflarger diameter than the maximum diameter of the tapered bore. Anannular bushing 47 fits into the tapered bore 460 and has an innerdiameter approximately equal to that of the intermediate bore portion46b.

The impeller 35 is secured on the shaft 12 by a stud bolt or screw 50which extends through the bore of the impeller and through bushing 47and is screwed into a tapped hole 51 in the end of the shaft 12. Thescrew 50 has a head portion 50a, a smooth cylindrical shank portion 50bhaving a diameter fitting the inner diameter of the bushing 47 and athreaded portion 500 having threads matching those of the tapped hole51. A washer 52 of hard durable material such as stainless steel isinterposed between the head 50a of screw 50 and the outer end of thebushing 47. The washer 52 is of substantial thickness in an axialdirection and has an inner diameter closely fitting the shank portion ofthe screw and an outer diameter substantially equal to the diameter ofthe outer end portion of the bushing 47. The direction of the threads ofthe screw 50 and of the mating threads of the tapped hole 51 in the endof the shaft 12 is such that rotation of the shaft 12 in the directionin which it is normally driven tends to tighten the screw.

The cylindrical bore 46a of the impeller hub closely fits the endportion of shaft 12 so as to center the impeller accurately with respectto the shaft, but it does not fit sulficiently tightly to provide adriving connection between the shaft and impeller or to prevent movementof the impeller relative to the shaft in an axial direction. The axialposition of the impeller relative to the shaft so as to provide andmaintain close tolerances of the clearance 36 is provided by shimmingbetween the inner end of the propeller hub and the nut 21 screwed onto athreaded portion 12a of the shaft to secure the fan 18 in assembledposition as described above. Accordingly one or more shims 53 areinterposed as required between the nut 21 and the inner end of theimpeller hub to achieve the desired clearance. The impeller hub issecured on the shaft 12 and pressed tightly toward the nut 21 by thescrew 5% Because of high pressures generated when the impeller strikes asolid object, the shim 53 should be of hard durable material such asstainless steel rather than softer material such as brass.

A driving connection between the shaft 12 and the impeller of the pumpis provided by the bushing 47 and screw 50. The bushing 47 is formed ofelastomeric material which is hard and yet capable of flow and elasticdeformation under sumciently high forces. When the screw 5-) istightened, the pressure applied through the washer 52 wedges the bushing47 tightly in the tapered bore portion 460 of the impeller hub andcauses the bushing to grip tightly the shank portion of the screw. Thebushing is substantially fully confined by the impeller hub, screw andwasher 52 so as to prevent extrusion of the bushing material.

The bushing also provides an air-tight seal between the impeller hub andthe screw 50 to prevent the ingress of any air between the impeller andthe shaft during priming. In the final stages of priming there is a highvacuum in the impeller chamber and anything less than a completelygas-tight seal would permit air to enter and impair the primingcharacteristics of the pump.

The bushing 47 has an axial length approximately equal 1 to that of thetapered portion 460 of the bore in the impeller hub. The inner bore 47aof the bushing is cylindrical and of substantially the same diameter asthe shank of the screw 50. The outer periphery 47b of the bushing istapered to conform substantially with the taper of the bore portion 460of the impeller hub. The taper is preferably of the order of 5 todegrees relative to the axis of the bushing, and preferably about 6 or 7degrees. While the size and proportions of the bushing depend on thedesign of the particular pump in which it is used, it will usually havean axial length somewhat less than the inside diameter, but at least 50%of the diameter, and an outside diameter at the smaller end of the orderof 30% to 50% greater than the inside diameter. As an example, a bushingfor a 3 pump has an inside diameter of approximately 0.56 inch, aminimum outside diameter of approximately 0.77 inch, and a length ofinch with a taperrelative to the axis of approximately 6.5 degrees.

An elastomeric material suitable for the bushing 47 has thecharacteristics of being hard, tough, resilient, abrasion resistant, oilresistant, and air resistant, with a high load bearing capacity incompression and a high shear strength. It should preferably be free offillers which tend to restrict elastic strain. The material should alsopreferably have a sufficiently high co-etficient of friction withrespect 4 to the surfaces engaged by the bushing to inhibit slipping. Ithas been found that the bore of the impeller can have a conventionallymachined surface. Steel, stainless steel and chromium plated bolts havebeen found satisfactory for use as the screw 50.

It has been found that urethane compounds which have been compounded toprovide a high durc-meter are satisfactory for use as the bushing 47. Asan example, a urethane compound having the following characteristics hasbeen satisfactorily used:

Durometer (Shore A or D) D Tensile strength, p.s.i 6500 Elongation,percent 250 Modulus, L-lOO 4700 Impact resistance, ft.-lb./in 1.2 Tearstrength, lbs/in 1400 Compressive set (percent in 22 hrs. at 158 F.) 9

A pump having an impeller mounted in the manner shown and described hasbeen found to withstand repeated jamming by solid articles such as sparkplugs without material damage to the pump or engine. The elasticproperties of the bushing 47, despite the high durometer of the materialused, appear to cushion the impact sufficiently to avoid damage. Thereis no evidence of material abrasion or wear of the bushing indicative ofexcessive slipping. After repeated jamming tests, it appears that therehas been slight further tightening of the screw 50. A small amount ofextrusion of the bushing material may occur around the washer 52 despitethe hardness of the bushing and its almost complete confinement. Thedriving connection between the screw 50 and the impeller provided by thebushing 47 is sufficiently positive not only to prevent any slippage ofthe impeller in normal use, but also to permit unscrewing the screw5lleven after repeated jammingsby cushioned tangential hammer blows onthe impeller.

While the invention has been described with reference to a preferredembodiment shown by way of example in the drawing, it will be understoodthat the invention is in no way limited to the precise details ofconstruction shown and described, but may be modified within the scopeof the appended claims.

What I claim is:

1. A rotary pump for liquids which may contain solids, said pumpcomprising a casing having an impeller chamoer with intake and dischargepassages and a bore extending into said chamber, a shaft extendingthrough said bore and adapted to be driven, said shaft having a tappedaxial hole in its end and a shoulder spaced from the end, an impelleraccommodated in said chamber and having a hub portion with a boreincluding an inner cylindrical portion fitting the portion of said shaftbetween said end and said shoulder and a tapered outer portion extendingbeyond the end of said shaft, a tapered bushing of hard elastomericmaterial seated in said tapered bore portion and having a central hole,a screw extending through said bushing into said threaded hole in theshaft, said screw having a head portion bearing on an outer end of saidbushing to press said bushing axially inwardly in said tapered bore ofsaid impeller hub and thereby provide a driving connection between saidrotor and sltaft through said bushing, said driving connection beingnormally positive but permitting limited yielding to cushion the impactand avoid the breakage of parts in the event of a solid wedging betweensaid impeller and easing.

2. A rotary pump according to claim 1, in which said bore in saidimpeller hub has an intermediate cylindr cal portion of a diameter toclosely fit said screw and inhlbtt extrusion of the material of saidbushing axially inwardly along said bolt.

3. A rotary pump according to claim 1, further comprising means foraccurately positioning said impeller with espect to said shoulder onsaid shaft and for varying said 5 position selectively to locate saidimpeller with close clearances with respect to said casing.

4. A rotary pump according to claim 1, further comprising an annularwasher between said screw head and the outer end of said bushing, saidwasher having an inner diameter to closely fit said screw and an outerdiameter substantially equal to the diameter of the larger end of saidbushing, said Washer substantially confining the outer end of saidbushing against extrusion.

5. A rotary pump according to claim 1, in which said bushing has adurometer of the order of 75 on the Shore D scale.

6. A rotary pump according to claim 1, in which said bushing is formedof a hard, elastic urethane compound.

References Cited UNITED STATES PATENTS 2,669,938 2/1954 La Bour 103-1113,253,136 5/1966 Faul 287-5206 FOREIGN PATENTS 535,747 4/ 1941 GreatBritain. 329,480 6/ 1958 Switzerland.

HENRY F. RADUAZO, Primary Examiner.

1. A ROTARY PUMP FOR LIQUIDS WHICH MAY CONTAIN SOLIDS, SAID PUMPCOMPRISING A CASING BETWEEN AN IMPELLER CHAMBER WITH INTAKE ANDDISCHARGE PASSAGES AND A BORE EXTENDING INTO SAID CHAMBER, A SHAFTEXTENDING THROUGH SAID BORE AND ADAPTED TO BE DRIVEN, SAID SHAFT HAVINGA TAPPED AXIAL HOLE IN ITS END AND A SHOULDER SPACED FROM THE END, ANIMPELLER ACCOMMODATED IN SAID CHAMBER AND HAVING A HUB PORTION WITH ABORE INCLUDING AN INNER CYLINDRICAL PORTION FITTING THE PORTION OF SAIDSHAFT BETWEEN SAID END AND SAID SHOULDER AND A TAPPERED OUTER PORTIONEXTENDING BEYOND THE END OF SAID SHAFT, A TAPERED BUSHING OF HARDELASTOMERIC MATERIAL SEATED IN SAID TAPERED BORE PORTION AND HAVING ACENTRAL HOLE, A SCREW EXTENDING THROUGH SAID